1. Field of the Invention
The present invention relates to an imaging apparatus and a camera system that can perform photographing while causing a light emitting apparatus to emit light.
2. Description of the Related Art
To capture a still image by causing a light emitting apparatus such as a flash apparatus to emit light, conventional imaging apparatus and camera systems perform preliminary light emission (hereinafter, “pre-flash”) to measure object conditions such as exposure in advance before main light emission for real photographing (hereinafter, “main-flash”).
For example, Japanese Patent Application Laid-Open No. 2005-275265 discusses an imaging apparatus which acquires a photometric value when pre-flash is not executed and a photometric value when pre-flash is executed by a photometric sensor having a plurality of photometric areas, and performs weight calculation for a photometric value of each photometric area based on a ratio of the acquired photometric values to calculate a photometric value of the main light emission.
However, when a main light emission amount is calculated based on a photometric result at the time of pre-flash, the influence of a drop in peripheral illumination by a photometric optical system, which occurs due to a position of a lens, a focusing lens, or the photometric sensor, must be taken into account.
When a log sensor having a wide dynamic range is used for the photometric sensor, there is a high possibility that even when a drop in peripheral illumination occurs, a photometric value of a surrounding part will be within the dynamic range.
However, when a linear sensor such as a charge-coupled device (CCD) having a narrow dynamic range is used, the influence of a drop in peripheral illumination is larger than that of the photometric sensor having a wide dynamic range. For example, when a linear sensor of ten dynamic range levels is used, if a light amount drops by six levels while ten levels at the center, a dynamic range of only four levels can be acquired at the surrounding part. The degree of a light amount drop is represented by the number of levels, which corresponds to Additive system of Photographic Exposure (APEX) values.
As a result, when a main object is present in an area where a drop in peripheral illumination is occurred, if pre-flash is executed based on a light emission amount set with a center as a reference, a photometric value of the main object may too small to be within a dynamic range, disabling acquisition of an accurate photometric value of the main object. In such a case, calculation of an appropriate main light emission amount is difficult for the main object.